System and method for mapping navigation space to patient space in a medical procedure

ABSTRACT

An apparatus is provided that is visible by both a three dimensional (3D) scanner system of a medical navigation system and a camera of the medical navigation system. The apparatus comprises a rigid member and a plurality of markers attached to the rigid member. Each of the plurality of markers includes a reflective surface portion visible by the camera and a distinct identifiable portion visible by the 3D scanner system. The apparatus further includes a connector mechanism to connect the apparatus to a reference location. The apparatus is in a field of view of the 3D scanner system and the camera within a timeframe of the 3D scan.

TECHNICAL FIELD

The present disclosure is generally related to neurosurgical or medicalprocedures, and more specifically to a system and method for mappingnavigation space to patient space in a medical procedure.

BACKGROUND

In the field of medicine, imaging and image guidance are a significantcomponent of clinical care. From diagnosis and monitoring of disease, toplanning of the surgical approach, to guidance during procedures andfollow- up after the procedure is complete, imaging and image guidanceprovides effective and multifaceted treatment approaches, for a varietyof procedures, including surgery and radiation therapy. Targeted stemcell delivery, adaptive chemotherapy regimes, and radiation therapy areonly a few examples of procedures utilizing imaging guidance in themedical field.

Advanced imaging modalities such as Magnetic Resonance Imaging (“MRI”)have led to improved rates and accuracy of detection, diagnosis andstaging in several fields of medicine including neurology, where imagingof diseases such as brain cancer, stroke, Intra-Cerebral Hemorrhage(“ICH”), and neurodegenerative diseases, such as Parkinson's andAlzheimer's, are performed. As an imaging modality, MRI enablesthree-dimensional visualization of tissue with high contrast in softtissue without the use of ionizing radiation. This modality is oftenused in conjunction with other modalities such as Ultrasound (“US”),Positron Emission Tomography (“PET”) and Computed X-ray Tomography(“CT”), by examining the same tissue using the different physicalprincipals available with each modality. CT is often used to visualizeboney structures and blood vessels when used in conjunction with anintra-venous agent such as an iodinated contrast agent. MRI may also beperformed using a similar contrast agent, such as an intra-venousgadolinium based contrast agent which has pharmaco-kinetic propertiesthat enable visualization of tumors and break-down of the blood brainbarrier. These multi-modality solutions can provide varying degrees ofcontrast between different tissue types, tissue function, and diseasestates. Imaging modalities can be used in isolation, or in combinationto better differentiate and diagnose disease.

In neurosurgery, for example, brain tumors are typically excised throughan open craniotomy approach guided by imaging. The data collected inthese solutions typically consists of CT scans with an associatedcontrast agent, such as iodinated contrast agent, as well as MRI scanswith an associated contrast agent, such as gadolinium contrast agent.Also, optical imaging is often used in the form of a microscope todifferentiate the boundaries of the tumor from healthy tissue, known asthe peripheral zone. Tracking of instruments relative to the patient andthe associated imaging data is also often achieved by way of externalhardware systems such as mechanical arms, or radiofrequency or opticaltracking devices. As a set, these devices are commonly referred to assurgical navigation systems.

Three dimensional (3D) sensor systems are increasingly being used in awide array of applications, including medical procedures. These sensorsystems determine the shape and/or features of an object positioned in ascene of the sensor system's view. In recent years, many methods havebeen proposed for implementing 3D modeling systems that are capable ofacquiring fast and accurate high resolution 3D images of objects forvarious applications.

Triangulation based 3D sensor systems and methods typically have one ormore projectors as a light source for projecting onto a surface and oneor more cameras at a defined, typically rectified relative position fromthe projector for imaging the lighted surface. The camera and theprojector therefore have different optical paths, and the distancebetween them is referred to as the baseline. Through knowledge of thebaseline distance as well as projection and imaging angles, knowngeometric/triangulation equations are utilized to determine distance tothe imaged object. The main differences among the various triangulationmethods known in the art lie in the method of projection as well as thetype of light projected, typically structured light, and in the processof image decoding to obtain three dimensional data.

A 3D sensor system may be contemplated as a novel extension of asurgical navigation systems. One popular triangulation based 3D sensorsystem is created by Mantis Vision, which utilizes a single framestructured light active triangulation system to project infrared lightpatterns onto an environment. To capture 3D information, a projectoroverlays an infrared light pattern onto the scanning target. Then adigital camera and a depth sensor, synched to the projector, capturesthe scene with the light reflected by the object for at least thetimeframe of one frame of the 3D scan. The technology works even incomplete darkness, since it includes its own illumination; in brightenvironments the quality of the resulting image depends on the hardwareused.

During a medical procedure, navigation systems require a registration totransform between the physical position of the patient in the operatingroom and the volumetric image set (e.g., MRI/CT) being navigated to.Conventionally, this registration is done to the position of a referencetool, which is visible by the tracking system and stays fixed inposition and orientation relative to the patient throughout theprocedure.

This registration is typically accomplished through correspondence touchpoints (e.g., either fiducial or anatomic points). Such an approach toregistration has a number of disadvantages, including requiringfiducials to be placed before scans, requiring points to be identified,providing for a limited number of points, touch point collection issubject to user variability, and the physical stylus used for collectingthe points can deform or deflect patient skin position. Anotherconventional approach to collecting the touch points includes performinga surface tracing of the patient drawn as a line which is matched to theimage set surface contour using either a stylus pointer or a laserpointer. Such an approach to registration has a number of disadvantages,including providing for a limited number of points, and the physicalstylus can deform or deflect patient skin position. Yet anotherconventional approach to collecting the touch points includes using amask, which requires a high level of operator training and is operatordependent. This approach also provides only a limited number of points.

Other common limitations of the conventional approaches to registrationdiscussed above include a stylus that needs to remain visible to thetracking system, which not necessarily possible depending on a patient'ssurgical position or may introduce surgical restrictions that need to beaccounted in planning, and error accumulation where touch point ortracing collection is of low quality resulting in error propagationthrough subsequent steps of the registration. Further, using theconventional methods, if registration is lost, re-registration isdifficult if not possible to be completed again during surgery.

Therefore, there is a need for an improved system and method for mappingnavigation space to patient space in a medical procedure.

SUMMARY

One aspect of the present disclosure provides an apparatus that isvisible by both a three dimensional (3D) scanner system of a medicalnavigation system and a camera of the medical navigation system. Theapparatus comprises a rigid member and a plurality of markers attachedto the rigid member. Each of the plurality of markers includes areflective surface portion visible by the camera and a distinctidentifiable portion visible by the 3D scanner system. The apparatusfurther includes a connector mechanism to connect the apparatus to areference location. The apparatus is in a field of view of the 3Dscanner system and the camera within a timeframe of the 3D scan.

Another aspect of the present disclosure provides a method ofregistering a patient for a medical procedure with a medical navigationsystem using an apparatus visible by both a three dimensional (3D)scanner system of the medical navigation system and a camera of themedical navigation system. The method comprises generating and receiving3D scan data from the 3D scanner representative of a 3D scan of at leasta portion of the patient, the 3D scan including distinct identifiableportions of the apparatus visible by the 3D scanner system; generatingand receiving image data from the camera, the image data includingreflective surface portions of the apparatus visible by the camera;loading saved medical image data, the saved medical data includingpreoperative image data saved during a previous scan of at least aportion of the patient; and performing a transformation mapping tocreate a single unified virtual coordinate space based on the 3D scandata, the image data, and the medical image data.

A further understanding of the functional and advantageous aspects ofthe disclosure can be realized by reference to the following detaileddescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the drawings, in which:

FIG. 1 illustrates the insertion of an access port into a human brain,for providing access to internal brain tissue during a medicalprocedure;

FIG. 2 shows an exemplary navigation system to support minimallyinvasive access port-based surgery;

FIG. 3 is a block diagram illustrating a control and processing systemthat may be used in the navigation system shown in FIG. 2;

FIG. 4A is a flow chart illustrating a method involved in a surgicalprocedure using the navigation system of FIG. 2;

FIG. 4B is a flow chart illustrating a method of registering a patientfor a surgical procedure as outlined in FIG. 4A;

FIG. 5 illustrates a flow chart describing the use of multiple patientreference markers for registration;

FIG. 6 is a drawing illustrating a wearable apparatus that may be usedwith the systems shown in FIGS. 2 and 3;

FIG. 7 is another example of the wearable apparatus shown in FIG. 6;

FIG. 8 is another example of the wearable apparatus shown in FIG. 6 andattachable to a head of a patient; and

FIG. 9 is a flow chart illustrating a method of registering a patientfor a medical procedure with a medical navigation system using awearable apparatus.

DETAILED DESCRIPTION

Various embodiments and aspects of the disclosure will be described withreference to details discussed below. The following description anddrawings are illustrative of the disclosure and are not to be construedas limiting the disclosure. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentdisclosure. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present disclosure.

As used herein, the terms, “comprises” and “comprising” are to beconstrued as being inclusive and open ended, and not exclusive.Specifically, when used in the specification and claims, the terms,“comprises” and “comprising” and variations thereof mean the specifiedfeatures, steps or components are included. These terms are not to beinterpreted to exclude the presence of other features, steps orcomponents.

As used herein, the term “exemplary” means “serving as an example,instance, or illustration,” and should not be construed as preferred oradvantageous over other configurations disclosed herein.

As used herein, the terms “about”, “approximately”, and “substantially”are meant to cover variations that may exist in the upper and lowerlimits of the ranges of values, such as variations in properties,parameters, and dimensions. In one non-limiting example, the terms“about”, “approximately”, and “substantially” mean plus or minus 10percent or less.

Unless defined otherwise, all technical and scientific terms used hereinare intended to have the same meaning as commonly understood by one ofordinary skill in the art. Unless otherwise indicated, such as throughcontext, as used herein, the following terms are intended to have thefollowing meanings:

As used herein, the phrase “access port” refers to a cannula, conduit,sheath, port, tube, or other structure that is insertable into asubject, in order to provide access to internal tissue, organs, or otherbiological substances. In some embodiments, an access port may directlyexpose internal tissue, for example, via an opening or aperture at adistal end thereof, and/or via an opening or aperture at an intermediatelocation along a length thereof. In other embodiments, an access portmay provide indirect access, via one or more surfaces that aretransparent, or partially transparent, to one or more forms of energy orradiation, such as, but not limited to, electromagnetic waves andacoustic waves.

As used herein the phrase “intraoperative” refers to an action, process,method, event or step that occurs or is carried out during at least aportion of a medical procedure. Intraoperative, as defined herein, isnot limited to surgical procedures, and may refer to other types ofmedical procedures, such as diagnostic and therapeutic procedures.

Embodiments of the present disclosure provide imaging devices that areinsertable into a subject or patient for imaging internal tissues, andmethods of use thereof. Some embodiments of the present disclosurerelate to minimally invasive medical procedures that are performed viaan access port, whereby surgery, diagnostic imaging, therapy, or othermedical procedures (e.g. minimally invasive medical procedures) areperformed based on access to internal tissue through the access port.

The present disclosure is generally related to medical procedures,neurosurgery, and minimally invasive port-based surgery in specific.

In the example of a port-based surgery, a surgeon or robotic surgicalsystem may perform a surgical procedure involving tumor resection inwhich the residual tumor remaining after is minimized, while alsominimizing the trauma to the healthy white and grey matter of the brain.In such procedures, trauma may occur, for example, due to contact withthe access port, stress to the brain matter, unintentional impact withsurgical devices, and/or accidental resection of healthy tissue. A keyto minimizing trauma is ensuring that the spatial location of thepatient as understood by the surgeon and the surgical system is asaccurate as possible.

FIG. 1 illustrates the insertion of an access port into a human brain,for providing access to internal brain tissue during a medicalprocedure. In FIG. 1, access port 12 is inserted into a human brain 10,providing access to internal brain tissue. Access port 12 may includeinstruments such as catheters, surgical probes, or cylindrical portssuch as the NICO BrainPath. Surgical tools and instruments may then beinserted within the lumen of the access port in order to performsurgical, diagnostic or therapeutic procedures, such as resecting tumorsas necessary. The present disclosure applies equally well to catheters,DBS needles, a biopsy procedure, and also to biopsies and/or cathetersin other medical procedures performed on other parts of the body wherehead immobilization is needed.

In the example of a port-based surgery, a straight or linear access port12 is typically guided down a sulci path of the brain. Surgicalinstruments would then be inserted down the access port 12.

Optical tracking systems, which may be used in the medical procedure,track the position of a part of the instrument that is withinline-of-site of the optical tracking camera. These optical trackingsystems also require a reference to the patient to know where theinstrument is relative to the target (e.g., a tumor) of the medicalprocedure. These optical tracking systems require a knowledge of thedimensions of the instrument being tracked so that, for example, theoptical tracking system knows the position in space of a tip of amedical instrument relative to the tracking markers being tracked.

Referring to FIG. 2, an exemplary navigation system environment 200 isshown, which may be used to support navigated image-guided surgery. Asshown in FIG. 2, surgeon 201 conducts a surgery on a patient 202 in anoperating room (OR) environment. A medical navigation system 205comprising an equipment tower, tracking system, displays and trackedinstruments assist the surgeon 201 during his procedure. An operator 203is also present to operate, control and provide assistance for themedical navigation system 205.

Referring to FIG. 3, a block diagram is shown illustrating a control andprocessing system 300 that may be used in the medical navigation system200 shown in FIG. 2 (e.g., as part of the equipment tower). As shown inFIG. 3, in one example, control and processing system 300 may includeone or more processors 302, a memory 304, a system bus 306, one or moreinput/output interfaces 308, a communications interface 310, and storagedevice 312. Control and processing system 300 may be interfaced withother external devices, such as tracking system 321, data storage 342,and external user input and output devices 344, which may include, forexample, one or more of a display, keyboard, mouse, sensors attached tomedical equipment, foot pedal, and microphone and speaker. Data storage342 may be any suitable data storage device, such as a local or remotecomputing device (e.g. a computer, hard drive, digital media device, orserver) having a database stored thereon. In the example shown in FIG.3, data storage device 342 includes identification data 350 foridentifying one or more medical instruments 360 and configuration data352 that associates customized configuration parameters with one or moremedical instruments 360. Data storage device 342 may also includepreoperative image data 354 and/or medical procedure planning data 356.Although data storage device 342 is shown as a single device in FIG. 3,it will be understood that in other embodiments, data storage device 342may be provided as multiple storage devices.

Medical instruments 360 are identifiable by control and processing unit300. Medical instruments 360 may be connected to and controlled bycontrol and processing unit 300, or medical instruments 360 may beoperated or otherwise employed independent of control and processingunit 300. Tracking system 321 may be employed to track one or more ofmedical instruments 360 and spatially register the one or more trackedmedical instruments to an intraoperative reference frame. For example,medical instruments 360 may include tracking markers such as trackingspheres that may be recognizable by a tracking camera 307. In oneexample, the tracking camera 307 may be an infrared (IR) trackingcamera. In another example, as sheath placed over a medical instrument360 may be connected to and controlled by control and processing unit300.

Control and processing unit 300 may also interface with a number ofconfigurable devices, and may intraoperatively reconfigure one or moreof such devices based on configuration parameters obtained fromconfiguration data 352. Examples of devices 320, as shown in FIG. 3,include one or more external imaging devices 322, one or moreillumination devices 324, a robotic arm 305, one or more projectiondevices 328, a 3D scanner 309, and one or more displays 311.

Exemplary aspects of the disclosure can be implemented via processor(s)302 and/or memory 304. For example, the functionalities described hereincan be partially implemented via hardware logic in processor 302 andpartially using the instructions stored in memory 304, as one or moreprocessing modules or engines 370. Example processing modules include,but are not limited to, user interface engine 372, tracking module 374,motor controller 376, image processing engine 378, image registrationengine 380, procedure planning engine 382, navigation engine 384, andcontext analysis module 386. While the example processing modules areshown separately in FIG. 3, in one example the processing modules 370may be stored in the memory 304 and the processing modules may becollectively referred to as processing modules 370.

It is to be understood that the system is not intended to be limited tothe components shown in FIG. 3. One or more components of the controland processing system 300 may be provided as an external component ordevice. In one example, navigation module 384 may be provided as anexternal navigation system that is integrated with control andprocessing system 300.

Some embodiments may be implemented using processor 302 withoutadditional instructions stored in memory 304. Some embodiments may beimplemented using the instructions stored in memory 304 for execution byone or more general purpose microprocessors. Thus, the disclosure is notlimited to a specific configuration of hardware and/or software.

While some embodiments can be implemented in fully functioning computersand computer systems, various embodiments are capable of beingdistributed as a computing product in a variety of forms and are capableof being applied regardless of the particular type of machine orcomputer readable media used to actually effect the distribution.

According to one aspect of the present application, one purpose of thenavigation system 205, which may include control and processing unit300, is to provide tools to the neurosurgeon that will lead to the mostinformed, least damaging neurosurgical operations. In addition toremoval of brain tumors and intracranial hemorrhages (ICH), thenavigation system 205 can also be applied to a brain biopsy, afunctional/deep-brain stimulation, a catheter/shunt placement procedure,open craniotomies, endonasal/skull-based/ENT, spine procedures, andother parts of the body such as breast biopsies, liver biopsies, etc.While several examples have been provided, aspects of the presentdisclosure may be applied to any suitable medical procedure.

While one example of a navigation system 205 is provided that may beused with aspects of the present application, any suitable navigationsystem may be used, such as a navigation system using optical trackinginstead of infrared cameras.

Referring to FIG. 4A, a flow chart is shown illustrating a method 400 ofperforming a port-based surgical procedure using a navigation system,such as the medical navigation system 205 described in relation to FIG.2. At a first block 402, the port-based surgical plan is imported. Adetailed description of the process to create and select a surgical planis outlined in international publication WO/2014/139024, entitled“PLANNING, NAVIGATION AND SIMULATION SYSTEMS AND METHODS FOR MINIMALLYINVASIVE THERAPY”, which claims priority to U.S. Provisional PatentApplication Ser. Nos. 61/800,155 and 61/924,993, which are all herebyincorporated by reference in their entirety.

Once the plan has been imported into the navigation system at the block402, the patient is placed on a surgical bed. The head position isconfirmed with the patient plan in the navigation system (block 404),which in one example may be implemented by a computer or controllerforming part of the equipment tower.

Next, registration of the patient is initiated (block 406). The phrase“registration” or “image registration” refers to the process oftransforming different sets of data into one coordinate system. Data mayinclude multiple photographs, data from different sensors, times,depths, or viewpoints. The process of “registration” is used in thepresent application for medical imaging in which images from differentimaging modalities are co-registered. Registration is used in order tobe able to compare or integrate the data obtained from these differentmodalities to the patient in physical space.

Those skilled in the relevant arts will appreciate that there arenumerous registration techniques available and one or more of thetechniques may be applied to the present example. Non-limiting examplesinclude intensity-based methods that compare intensity patterns inimages via correlation metrics, while feature-based methods findcorrespondence between image features such as points, lines, andcontours. Image registration methods may also be classified according tothe transformation models they use to relate the target image space tothe reference image space. Another classification can be made betweensingle-modality and multi-modality methods. Single-modality methodstypically register images in the same modality acquired by the samescanner or sensor type, for example, a series of magnetic resonance (MR)images may be co-registered, while multi-modality registration methodsare used to register images acquired by different scanner or sensortypes, for example in magnetic resonance imaging (MRI) and positronemission tomography (PET). In the present disclosure, multi-modalityregistration methods may be used in medical imaging of the head and/orbrain as images of a subject are frequently obtained from differentscanners. Examples include registration of brain computerized tomography(CT)/MRI images or PET/CT images for tumor localization, registration ofcontrast-enhanced CT images against non-contrast-enhanced CT images, andregistration of ultrasound and CT to patient in physical space.

Referring now to FIG. 4B, a flow chart is shown illustrating a methodinvolved in registration block 406 as outlined in FIG. 4A, in greaterdetail. If the use of fiducial touch points (440) is contemplated, themethod involves first identifying fiducials on images (block 442), thentouching the touch points with a tracked instrument (block 444). Next,the navigation system computes the registration to reference markers(block 446).

Alternately, registration can also be completed by conducting a surfacescan procedure (block 450), which may be applied to aspects of thepresent disclosure. The block 450 is presented to show an alternativeapproach. First, the face is scanned using a 3D scanner (block 452).Next, the face surface is extracted from MR/CT data (block 454).Finally, surfaces are matched to determine registration data points(block 456).

Upon completion of either the fiducial touch points (440) or surfacescan (450) procedures, the data extracted is computed and used toconfirm registration at block 408, shown in FIG. 4A.

Referring back to FIG. 4A, once registration is confirmed (block 408),the patient is draped (block 410). Typically, draping involves coveringthe patient and surrounding areas with a sterile barrier to create andmaintain a sterile field during the surgical procedure. The purpose ofdraping is to eliminate the passage of microorganisms (e.g., bacteria)between non-sterile and sterile areas. At this point, conventionalnavigation systems require that the non-sterile patient reference isreplaced with a sterile patient reference of identical geometry locationand orientation. Numerous mechanical methods may be used to minimize thedisplacement of the new sterile patient reference relative to thenon-sterile one that was used for registration but it is inevitable thatsome error will exist. This error directly translates into registrationerror between the surgical field and pre-surgical images. In fact, thefurther away points of interest are from the patient reference, theworse the error will be.

Upon completion of draping (block 410), the patient engagement pointsare confirmed (block 412) and then the craniotomy is prepared andplanned (block 414).

Upon completion of the preparation and planning of the craniotomy (block414), the craniotomy is cut and a bone flap is temporarily removed fromthe skull to access the brain (block 416). Registration data is updatedwith the navigation system at this point (block 422).

Next, the engagement within craniotomy and the motion range areconfirmed (block 418). Next, the procedure advances to cutting the duraat the engagement points and identifying the sulcus (block 420).

Thereafter, the cannulation process is initiated (block 424).Cannulation involves inserting a port into the brain, typically along asulci path as identified at 420, along a trajectory plan. Cannulation istypically an iterative process that involves repeating the steps ofaligning the port on engagement and setting the planned trajectory(block 432) and then cannulating to the target depth (block 434) untilthe complete trajectory plan is executed (block 424).

Once cannulation is complete, the surgeon then performs resection (block426) to remove part of the brain and/or tumor of interest. The surgeonthen decannulates (block 428) by removing the port and any trackinginstruments from the brain. Finally, the surgeon closes the dura andcompletes the craniotomy (block 430). Some aspects of FIG. 4A arespecific to port-based surgery, such as portions of blocks 428, 420, and434, but the appropriate portions of these blocks may be skipped orsuitably modified when performing non-port based surgery.

Referring now to FIG. 5, a registration process, similar to that whichmay be used in block 456 of FIG. 4B, is shown for creating a commoncoordinate space composed of amalgamated virtual and actual coordinatespaces. The common coordinate space may be composed of both an actualcoordinate space and a virtual coordinate space, where the actualcoordinate space contains actual objects that exist in space and thevirtual coordinate space contains virtual objects that are generated ina virtual space. The common coordinate space containing both theaforementioned actual and virtual objects may be produced as follows.

In order to form a common coordinate space composed of the amalgamatedvirtual and actual coordinate spaces, the two spaces may be coupled witha “common reference coordinate”, having a defined position that can belocated in both the actual and virtual coordinate spaces. An example ofsuch a common reference coordinate 500 and actual and virtual coordinatespace origins, 510 and 520, are provided in FIG. 5. Once the commonreference coordinate position is acquired in both spaces they can beused to correlate the position of any point in one coordinate space tothe other. The correlation is determined by equating the locations ofthe common reference coordinate in both spaces and solving for anunknown translation variable for each degree of freedom defined in thetwo coordinate spaces. These translation variables may then be used totransform a coordinate element of a position in one space to anequivalent coordinate element of a position in the other. An examplecorrelation can be derived from the diagram in FIG. 5 depicting a twodimensional coordinate space. In FIG. 5, the common referencecoordinates 500 position is determined relative to the actual coordinatespace origin 510 and the virtual coordinate space origin 520. The commonreference coordinates positions can be derived from the diagram asfollows:

(X _(cra) , Y _(cra))=(55, 55)

and

(X _(crv) , Y _(crv))=(−25, −45)

Where the subscript “cra” denotes the common reference coordinateposition relative to the actual coordinate space origin and thesubscript “crv” denotes the common reference coordinate positionrelative to the virtual coordinate space origin. Utilizing a generictranslation equation describing any points ((Y_(a), X_(a)) and (Y_(v),X_(v))), where the subscript “a” denotes the coordinates of a pointrelative to the actual coordinate space origin 510, and the subscript“v” denotes the coordinate of a point relative to the virtual coordinatespace origin 520, we can equate the individual coordinates from eachspace to solve for translation variables ((Y_(T), X_(T))), where thesubscript “T” denotes the translation variable as shown below.

Y _(a) =Y _(v) +Y _(T)

X _(a) =X _(v) +X _(T)

Now substituting the derived values of our points from FIG. 5 we cansolve for the translation variable.

55=−45+Y _(T)

100=Y_(T)

and

55=−25+X _(T)

80=X_(T)

Utilizing this translation variable, any point ((i.e. (Y_(v), X_(v))) inthe virtual coordinate space may be transformed into an equivalent pointin the actual coordinate space through the two generic transformationequations provided below. It should be noted that these equations can berearranged to transform any coordinate element of a position from theactual coordinate space into an equivalent coordinate element of aposition in the virtual coordinate space as well.

Y _(a) =Y _(v)+100

and

X _(a) =X _(v)+80

This will allow both the virtual and actual objects respective positionsto therefore be defined in both the actual and virtual coordinate spacessimultaneously. Once the correlation is determined the actual andvirtual coordinate spaces become coupled and the result in the formationof a common coordinate space that may be used to register virtual andactual objects. It should be noted that these virtual and actual objectscan be superimposed in the common coordinate space (e.g., they canoccupy the same coordinates simultaneously).

According to one aspect of the present application, using a handheldthree dimensional (3D) surface scanner system, such as the 3D scanner309, a full or nearly full array scan of a patient's surface can beachieved, as opposed to 1D line or a 2D grid of point depths with theconventional approaches. This may provide an order of magnitude greaterpoint information than the surface tracing methods used in conventionalapproaches. Using a dense point cloud provided by the 3D scanner 309,this point cloud may be mapped to the extracted surface of the MR/CTvolumetric scan data (e.g., the pre-op image data 354) to register thepatient's physical position to the volumetric data. The tracking system321 (e.g., part of the navigation system 200) has no reference to thepoint cloud data. Therefore a tool may be provided that is visible toboth the tracking system 321 and the 3D scanner 309. A transformationbetween the tracking system's camera space and the 3D scanner space maybe identified so that the point cloud provided by the 3D scanner 309 andthe tracking system 321 can be registered to the patient space. Atransformation similar to or based on the transformation described inconnection with FIG. 5 may be used.

One aspect of the present application provides a tracking tool at leastpartially optimized for visibility and tracking by both the trackingsystem 321 and a 3D scanner system, such as the 3D scanner 309. In oneexample, the 3D scanner 309 may be a colour 3D scanner. The 3D scanner309 may be used to collect a colour point cloud which is defined in thepatient space. To determine a transformation mapping between thetracking system 321 and the patient space, the tracking tool may beidentifiable in both spaces. While there may be guidelines for tooldesign compatibility with the tracking system 321, no such rules existfor creating targets for extraction within point clouds. In one example,a cross-compatible tool may be designed using three retro-reflectivecircular targets placed at unique distances from one another on a singlerigid plane. Each target may include an IR retro-reflective center forvisibility by the tracking system 321 and is surrounded by a highcontrast coloured ring which enables straight forward extraction fromthe output point cloud collected from the 3D scanner 309.

Referring now to FIGS. 6, 7, and 8, FIG. 6 is a drawing illustrating awearable apparatus 600 that may be used with the systems shown in FIGS.2 and 3. FIG. 7 is another example of the wearable apparatus 600 shownin FIG. 6. FIG. 8 is another example of the wearable apparatus 600 shownin FIG. 6 and attachable to a head of a patient. FIGS. 6-8 will now bedescribed simultaneously, with like elements being referred to with likereference numerals.

The apparatus 600 may be visible by both a three dimensional (3D)scanner system (e.g., 3D scanner 309) of a medical navigation system,such as the medical navigation system 205, and a camera of the medicalnavigation system 205, such as camera 307. In one example, the apparatus600 may be wearable. The wearable apparatus includes a rigid member 602and a plurality of markers 604 attached to the rigid member 602. Each ofthe plurality of markers 604 includes a reflective surface portion 606visible by the camera 307 and a distinct identifiable portion 608visible by the 3D scanner 309. In one example, the distinct identifiableportion 608 may be a distinct colour portion. The wearable apparatus 600further has a connector mechanism (not shown) to connect the apparatus600 to a reference location. The apparatus may be located in a field ofview of the 3D scanner system and the camera within a timeframe of the3D scan.

In one example, the timeframe may be at least one frame of the 3D scan.The reference location may be a fixed location, such as on a Mayfieldclamp, a bed, or a stretcher. Alternatively, the reference locationincludes being attached onto a patient, either simply resting on thepatient for a short time during at least one frame of the 3D scan, orfixed to the patient, for example using medical grade tape, an adhesive,Velcro, or any other suitable fastener. The apparatus may besterilizable. The field of view may also include a patient reference.

In one example, the wearable apparatus 600 may have at least threemarkers 604. However, any number of markers 604 may be used to meet thedesign criteria of a particular application. The rigid member 602 may bea rigid surface member with at least three markers 604 mounted thereon.In one example, the rigid member 602 may be planar and substantiallyrigid in shape. The reflective surface portions 606 may include anidentifiable surface, which in one example may be a retroreflectivesurface. In FIGS. 6-8, the rigid member 602 is shown to be in theapproximate shape of a triangle. However, any suitable shape may be usedto meet the design criteria of a particular application.

In one example, the apparatus 600 may take the form of a flexible (e.g.,non-rigid) cap or bandage that may be either placed on, stuck to, oraffixed to the patient 202. In one example, the markers 604 on thebandage could be placed in a geometric position to represent a validtracking tool having reflective markers. In one example, such a bandagemay be recognizable by tracking system 321 of the medical navigationsystem 205 (e.g., defined in ROM file saved in data storage device 342)and recognized as a valid trackable tool by the tracking system 321.

In one example, at least three markers 604 may be all mounted on therigid member 602 at unique distances from each other with the distinctidentifiable portion 608 of each of the markers 604 being a distinctcolour from the others of the markers 604. In another example, at leastthree markers 604 may be all mounted on the rigid member 602 at uniquedistances from each other with the distinct identifiable portion 608 ofeach of the three markers 604 being the same colour but distinct incolour from the rigid member 602.

In one example, each of the plurality of markers 604 may include a firstidentifiable shape and a second larger identifiable shape around thefirst identifiable shape where the first identifiable shape includes thereflective surface portion 606 and the second identifiable shapeincludes the distinct identifiable portion 608. In one example, thefirst identifiable shape may be a circle and the second identifiableshape may be a circular ring. While circular shapes and circular ringsare provided as example shapes for the reflective surface portion 606and the distinct identifiable portion 604, any suitable shapes may beused to meet the design criteria of a particular application. Thecircular design of the markers 604 may allow for orientation independentadhesion while the unique spacing between markers 604 allows for realtime tracking of the overall tool 600 orientation.

In one example, the wearable apparatus 600 further has a strap 610 (FIG.8) connected to the rigid member 602 for securing the wearable apparatus600 to a patient. In one example, the strap 610 is attachable around ahead 612 of the patient. In another example, the wearable apparatus 600is securable to a patient using a medical adhesive. While the strap 610and a medical adhesive have been provided as examples, any suitablefastening means may be used to attach the apparatus 600 to the patient202. The apparatus 600 may be designed such that the apparatus or tool600 may be attached in a variety of ways based on the adhesive used.Some examples for placement are attaching the apparatus 600 to aheadband or directly to the shaved head 612 surface using medicaladhesive. In another example, as described above, the apparatus 600 maytake the form of a flexible bandage having an adhesive on the back sidefor affixing to the patient 202.

Following the target extraction in both the tracking system 321 spaceand 3D scanner 309 space, a transformation mapping can be modeled torelate the tracking system 321 space with the 3D scanner 309 space. Oncethe 3D scanner 309 point cloud is mapped to the MR/CT coordinates byapplying a surface matching method between an extracted surface of theMR/CT to the point cloud, the apparatus 600 transformation allowsregistration between the tracking system 321 and the MR/CT image data.

Conventional approaches use a reference star that has five positioningtargets that are retro-reflective with no additional colour that can beseen by the 3D scanner and the infrared optical tracking system. Incontrast, the apparatus 600 has, in one example, only 3 markers 604 anduses substantially flat targets 604. The conventional reference staralso uses larger distances between positioning targets and is placedbeside the patient 202 and not on the patient 202.

Retro-reflective markers are also used by some 3D scanners as passivemarkers to assist with stitching individual frames within a point cloudand improve overall accuracy of 3D scans. Two examples of companies thatsell target stickers as part of their 3D scanner portfolio are Creaformand LabelID.

Referring now to FIG. 9, a flow chart is shown illustrating a method 900of registering a patient for a medical procedure with a medicalnavigation system using a wearable apparatus, such as the wearableapparatus 600. The method 900 may register a patient for a medicalprocedure with a medical navigation system, such as the medicalnavigation system 205, using a wearable apparatus (e.g., the apparatus600) visible by both a three dimensional (3D) scanner system (e.g.,including the 3D scanner 309) of the medical navigation system 205 and acamera (e.g., the camera 307) of the medical navigation system 205. Themethod may be controlled and/or executed, for example by the processor302 of the control and processing unit 300 that forms part of themedical navigation system 205.

At a first block 902, the method 900 generates and receives 3D scan datafrom the 3D scanner 309 that is representative of a 3D scan of at leasta portion of the patient 202. The 3D scan includes distinct identifiableportions of the wearable apparatus 600 that are visible by the 3Dscanner 309. In one example, the distinct identifiable portions may bethe distinct colour portions 608.

Next, at a block 904, the method 900 generates and receives image datafrom the camera 307. The image data includes reflective surface portionsof the wearable apparatus 600 visible by the camera 307. In one example,the reflective surface portions may be the reflective surface portions606.

Next, at a block 906, the method 900 loads saved medical image data. Thesaved medical data includes preoperative image data, such as the pre-opimage data 354, saved during a previous scan of at least a portion ofthe patient 202. The pre-op image data 354 may include data fromcomputerized tomography (CT) images, magnetic resonance imaging (MRI)images, positron emission topography (PET) images, contrast-enhanced CTimages, X-ray images, ultrasound images, or any other suitable medicalimaging source.

While the blocks 902, 904, and 906 are shown as being performed in aparticular order, blocks 902, 904, and 906 may be performed in anysuitable order, including concurrently.

Next, at a block 908, the method 900 performs a transformation mappingto create a single unified virtual coordinate space based on the 3D scandata, the image data, and the medical image data. In one example, thetransformation may be similar to or based on the registration processdescribed in connection with FIG. 5. In another example, thetransformation mapping includes a surface matching approach using a 3Dscanner point cloud based on the 3D scan data and at least one of MR andCT coordinates. In another example, the camera 307 of the medicalnavigation system 205 may form part of a tracking system, such as thetracking system 321, and the transformation mapping may further includeregistering the tracking system 321 to create a single unified virtualcoordinate space for the 3D scanner point cloud, at least one of the MRand CT coordinates, and the image data from the tracking system. Howeverany suitable known or yet to be developed transformation process may beapplied.

In one slightly modified example, the 3D scanner 309 may be affixed toan end effector of a robot, such as the robotic arm 305. The robotic arm305 may also have tracking markers affixed thereto that are visible by acamera, such as the camera 307, of the tracking system 321. The roboticarm 305 may perform the 3D scan (e.g., block 902). Since the position ofthe robotic arm 305, and consequently the 3D scanner position, are knownto the tracking system 321 (e.g., as a result of block 904), and sincethe distance from the 3D scanner to the patient 202 being scanned can becalculated by the processing unit 300 using the data from the 3Dscanner, a starting point cloud can be generated at a known positionrelative to the tracking markers affixed to the robotic arm 305.Subsequently, the 3D scanner 309 can be moved free- hand by a doctor ortechnician without the need to be tracked by the tracking system 321,which allows the 3D scanner to be moved out of line of sight of thetracking system 321 camera 307. The subsequent point clouds may bestitched onto the starting point cloud resulting in a complete surfacein a known location relative to the tracking system 321. This surfacecan then be registered to the surface of MRI data (e.g., the block 309performing the transformation mapping) resulting in a completetransformation from the MRI data to the tracking system 321. In anotherexample, two separate 3D scanners may be used, one that remains fixed tothe robotic arm 305 and one that may be used free hand by a doctor ortechnician. In this approach, the 3D scanner on the end effector of therobotic arm 305 exists at a fixed point and can be used to generate thecloud point to tracking system 321 coordinates. Subsequently data fromthe free- hand 3D scanner can be used to register new frames to originalframes from the fixed 3D scanner data using continuously stitching.

In one example, the wearable apparatus 600 includes a plurality ofmarkers 604 attached to a rigid member 602 of the wearable apparatus600, where each of the plurality of markers 604 includes one of thereflective surface portions 606 visible by the camera 309 and one of thedistinct identifiable portions 608 visible by the 3D scanner 309. In oneexample, the wearable apparatus 600 has at least three markers 604 andthe rigid member 602 is a substantially rigid surface with the at leastthree markers 604 mounted thereon.

In one example, at least three markers 604 may be all mounted on therigid member 602 at unique distances from each other with the distinctidentifiable portion 608 of each of the markers 604 being a distinctcolour from the others of the markers 604. In another example, at leastthree markers 604 may be all mounted on the rigid member 602 at uniquedistances from each other with the distinct identifiable portion 608 ofeach of the three markers 604 being the same colour but distinct incolour from the rigid member 602.

In one example, each of the plurality of markers 604 may include a firstidentifiable shape and a second larger identifiable shape around thefirst identifiable shape where the first identifiable shape includes thereflective surface portion 606 and the second larger identifiable shapeincludes the distinct identifiable portion 604. In one example, thefirst identifiable shape may be a circle and the second largeridentifiable shape may be a circular ring. While circular shapes andcircular rings are provided as example shapes for the reflective surfaceportion 606 and the distinct identifiable portion 604, any suitableshapes may be used to meet the design criteria of a particularapplication. The circular design of the markers 604 may allow fororientation independent adhesion while the unique spacing betweenmarkers 604 allows for real time tracking of the overall tool 600orientation.

In one example, the wearable apparatus 600 further has a strap 610 (FIG.8) connected to the rigid member 602 for securing the wearable apparatus600 to a patient. In one example, the strap 610 is attachable around ahead 612 of the patient. In another example, the wearable apparatus 600is securable to a patient using a medical adhesive. While the strap 610and a medical adhesive have been provided as examples, any suitablefastening means may be used to attach the apparatus 600 to the patient202. The apparatus 600 may be designed such that the apparatus or tool600 may be attached in a variety of ways based on the adhesive used.Some examples for placement are attaching the apparatus 600 to aheadband or directly to the shaved head 612 surface using medicaladhesive.

In one example, the apparatus 600 may take the form of a flexible (e.g.,non-rigid) cap or bandage that may be either placed on, stuck to, oraffixed to the patient 202. In one example, the markers 604 on thebandage could be placed in a geometric position to represent a validtracking tool having reflective markers. In one example, such a bandagemay be recognizable by tracking system 321 of the medical navigationsystem 205 (e.g., defined in ROM file saved in data storage device 342)and recognized as a valid trackable tool by the tracking system 321.

The specific embodiments described above have been shown by way ofexample, and it should be understood that these embodiments may besusceptible to various modifications and alternative forms. It should befurther understood that the claims are not intended to be limited to theparticular forms disclosed, but rather to cover modifications,equivalents, and alternatives falling within the spirit and scope ofthis disclosure.

1. An apparatus, for use in a medical navigation system, visible by botha three dimensional (3D) scanner system and a camera of a trackingsystem, the apparatus comprising: a rigid member; a plurality of markersattached to the rigid member, each of the plurality of markersincluding: a reflective surface portion visible by the camera to enablecapture of image data by the tracking system in a tracking space; and adistinct identifiable portion visible by the 3D scanner system to enablecapture of 3D scan data by the 3D scanner system independently of thetracking system in a 3D scanner space different from the tracking space;and a connector mechanism to connect the apparatus to a referencelocation.
 2. The apparatus according to claim 1, wherein the apparatuscomprises at least three markers.
 3. The apparatus according to claim 1,wherein the rigid member is substantially rigid and planar in shape andthe reflective surface portion includes a surface identifiable by thecamera.
 4. The apparatus according to claim 1, wherein the plurality ofmarkers are all attached to the rigid member at unique distances fromeach other, and the distinct identifiable portion of each of theplurality of markers is a distinct colour from the others of theplurality of markers.
 5. The apparatus according to claim 1, wherein theplurality of markers are all attached to the rigid member at uniquedistances from each other, and the distinct identifiable portion of eachof the plurality of markers is the same colour for each of the pluralityof markers, the same colour being distinct from a colour of the rigidmember.
 6. The apparatus according to claim 1, wherein each of theplurality of markers includes a first identifiable shape and a largersecond identifiable shape around the first identifiable shape.
 7. Theapparatus according to claim 6, wherein the first identifiable shapeincludes the reflective surface portion and the second identifiableshape includes the distinct identifiable portion.
 8. The apparatusaccording to claim 1, wherein the apparatus further comprises: a strapconnected to the rigid member for securing the apparatus to a patient.9. The apparatus according to claim 8, wherein the strap is attachablearound a head of the patient.
 10. The apparatus according to claim 1,wherein the apparatus is securable to a patient using a medicaladhesive.
 11. The apparatus according to claim 1, wherein the rigidmember is coupled to a flexible member that is attachable to a patient.12. The apparatus according to claim 11, wherein the flexible membercomprises at least one of a bandage and a sticker.
 13. The apparatusaccording to claim 1, wherein the reference location comprises at leastone of a fixed location on a Mayfield clamp, a bed, and a stretcher. 14.The apparatus according to claim 1, wherein the reference locationincludes a portion of a patient.
 15. The apparatus according to claim 1,wherein the apparatus is wearable.
 16. The apparatus according to claim1, wherein the apparatus is sterilizable.
 17. A method of registering apatient for a medical procedure with a medical navigation system usingan apparatus visible by both a three dimensional (3D) scanner system anda camera of a tracking system, the 3D scanner system having an unknownposition relative to the camera and the tracking system, the methodcomprising: generating and receiving 3D scan data from the 3D scannersystem representative of a 3D scan of at least a portion of the patient,the 3D scan including distinct identifiable portions of the apparatusvisible by the 3D scanner system in a 3D scanner space; generating andreceiving image data from the camera, the image data includingreflective surface portions of the apparatus visible by the camera in atracking space different from the 3D scanner space; loading savedmedical image data, the saved medical data including preoperative imagedata saved during a previous scan of at least a portion of the patient;and performing a transformation mapping to create a single unifiedvirtual coordinate space based on the 3D scan data, the image data, andthe medical image data, the transformation mapping including performinga first mapping to map one of the 3D scan data, the image data, and themedical image data to a second of the 3D scan data, the image data, andthe medical image data, and performing a second mapping to map a thirdof the 3D scan data, the image data, and the medical image data to thefirst mapping.
 18. The method according to claim 17, wherein thedistinct identifiable portions are distinct colour portions.
 19. Themethod according to claim 17, wherein the apparatus includes a pluralityof markers attached to a rigid member of the apparatus, each of theplurality of markers including one of the reflective surface portionsvisible by the camera and one of the distinct identifiable portionsvisible by the 3D scanner system.
 20. The method according to claim 19,wherein the apparatus comprises at least three markers, the rigid memberbeing a substantially rigid planar surface with the at least threemarkers mounted thereon.
 21. The method according to claim 19, whereinthe plurality of markers are all mounted on the rigid member at uniquedistances from each other, and the distinct identifiable portions ofeach of the plurality of markers is a distinct colour from the others ofthe plurality of markers.
 22. The method according to claim 19, whereinthe plurality of markers are all mounted on the rigid member at uniquedistances from each other, and the distinct identifiable portion of eachof the plurality of markers is the same colour for each of the pluralityof markers, the same colour being distinct from a colour of the rigidmember.
 23. The method according to claim 17, wherein the reflectivesurface portions include surfaces identifiable by the camera, each ofthe markers includes a first identifiable shape and a larger secondidentifiable shape around the first identifiable shape, and the firstidentifiable shape includes the reflective surface portion and thesecond identifiable shape includes the distinct identifiable portion.24. The method according to claim 17, wherein the apparatus furthercomprises a strap connected to the rigid member for securing theapparatus to the patient, the strap is attachable around a head of thepatient, and the at least a portion of the patient includes at least aportion of the head of the patient.
 25. The method according to claim17, wherein the apparatus is securable to a patient using a medicaladhesive.
 26. The method according to claim 17, wherein the savedmedical image data includes at least one of magnetic resonance (MR)coordinates taken from a MR scan and computed tomography (CT)coordinates taken from a CT scan.
 27. The method according to claim 26,wherein the transformation mapping includes a surface matching approachusing a 3D scanner point cloud based on the 3D scan data and at leastone of the MR and CT coordinates.
 28. The method according to claim 27,wherein the transformation mapping further includes registering thetracking system to create a single unified virtual coordinate space forthe 3D scanner point cloud, at least one of the MR and CT coordinates,and the image data from the tracking system.
 29. The method according toclaim 17, wherein the preoperative image data includes data from atleast one of computerized tomography (CT) images, magnetic resonanceimaging (MRI) images, positron emission topography (PET) images,contrast-enhanced CT images, X-ray images, and ultrasound images.